Researchers working to discover why African Americans disproportionately suffer from asthma are planning to map the genetic code of 1,000 people of African descent in four years.

The Johns Hopkins-led team of experts in genetics, immunology, epidemiology and allergic disease want to know why up to 20 percent of black people have asthma. The disease afflicts 20 million Americans, causes difficultly breathing, wheezing and tightness in the chest and can lead to hospitalization and death.

The work “represents an exciting opportunity to disentangle the genetic basis of a host of other diseases, not just asthma, which have a hereditary component and uniquely or disproportionately affect minorities,” said the study’s principal investigator Kathleen Barnes, a professor in the Division of Allergy and Clinical Immunology in Hopkins’ School of Medicine and the Bloomberg School of Public Health, in a statement.

The study of 500 asthmatics and 500 non-asthmatics from 19 U.S., Caribbean, South American and Western African academic researcher centers aims to identify genetic variations that may be associated with elevated disease risk.